Supramolecular Assembly Based on Calix(4)arene and Aggregation-Induced Emission Photosensitizer for Phototherapy of Drug-Resistant Bacteria and Skin Flap Transplantation.

Photodynamic therapy as a burgeoning and non-invasive theranostic technique has drawn great attention in the field of antibacterial treatment but often encounters undesired phototoxicity of photosensitizers during systemic circulation. Herein, a supramolecular substitution strategy is proposed for phototherapy of drug-resistant bacteria and skin flap repair by using macrocyclic p-sulfonatocalix(4)arene (SC4A) as a host, and two cationic aggregation-induced emission luminogens (AIEgens), namely TPE-QAS and TPE-2QAS, bearing quaternary ammonium group(s) as guests. Through host-guest assembly, the obtained complex exhibits obvious blue fluorescence in the solution due to the restriction of free motion of AIEgens and drastically inhibits efficient type I ROS generation. Then, upon the addition of another guest 4,4'-benzidine dihydrochloride, TPE-QAS can be competitively replaced from the cavity of SC4A to restore its pristine ROS efficiency and photoactivity in aqueous solution. The dissociative TPE-QAS shows a high bacterial binding ability with an efficient treatment for methicillin-resistant Staphylococcus aureus (MRSA) in dark and light irradiation. Meanwhile, it also exhibits an improved survival rate for MRSA-infected skin flap transplantation and largely accelerates the healing process. Thus, such cascaded host-guest assembly is an ideal platform for phototheranostics research.

Water contaminant: Use it but do not shield it to synthesize co-polymers with multiple emission colours.

Due to the high affinity with water molecules, amide compounds are easily contaminated by moisture; therefore, the water interference effect cannot be totally excluded from the amide-involved reactions. Thus, the perfect solution is to use the interference effect but not shield it in a real application. In this work, we introduced different contents of sodium acrylate (AAS) to scavenge water from the monomers of N-isopropylacrylamide (NIPAm) when copolymerized with TPA-Vinyl-4CN. Herein, water molecules play a role as nucleophilic reagents to attack highly active functional groups as -C=C-CN from TPA-Vinyl-4CN, leading to a blue emissive TPA-Vinyl-2CHO. From this study, we made a deep awareness of the interactions between three reaction partners of AAS and NIPAm as well as TPA-Vinyl-4CN. Our results clearly demonstrated the fact that water can be perfectly used and controlled by the water absorbent of AAS, developing a new approach to synthesizing multiple emission-coloured polymers by using only one luminogen of TPA-Vinyl-4CN.

A fluorescent quaternary phosphonium main-chain-type polymer: an opportunity to fabricate functional materials with excellent antibacterial activity and bacterial imaging capability.

The large-scale transmission and infection of pathogens worldwide have encouraged scientists to develop new antibacterial agents that do not succumb to bacterial resistance, which is not only of significant research interest but also challenging. In this work, we fabricated two main-chain (MC)-type cationic polymers (TPE-ammonium polymer and TPE-phosphonium polymer) through a one-step 100% atomic economic reaction. The two polymers demonstrated very promising antibacterial activity and their minimal inhibitory concentration (MIC) values are lower than that of most previously reported antibacterial agents. Especially, the phosphonium-doped MC polymer exhibited very small MICs of 0.24 and 0.98 µg mL-1 against S. aureus and E. coli, respectively. This excellent antibacterial performance by the TPE-phosphonium polymer is attributed to the advantages of the MC-type polymer such as its large molecular weight (Mn = 103 011) and stronger polarization effect from the P atom. More impressively, depending on the typical aggregation-induced emission (AIE) property and excellent antibacterial behaviors, the TPE-phosphonium polymer was successfully used for bacterial imaging and real-time monitoring of bacterial viability.

Visualization of Enantiorecognition and Resolution by Chiral AIEgens.

Enantioselective recognition and separation have attracted much attention in pharmaceutical analysis, food chemistry, and life science. Herein, we propose an efficient strategy to achieve such purposes using optically active luminogens with aggregation-induced emission (AIE) characteristics. These AIE luminogens (AIEgens) show strong enantiomeric discrimination for 12 kinds of chiral acids and unprotected amino acids. In particular, an exceptionally high enantioselectivity for d/l-Boc-glutamic acid was observed, as demonstrated by the large difference between the formed AIEgen/acid complexes. Due to the AIE effect, enantioselective separation was achieved by aggregation of the AIEgens with one enantiomer in the mixed acid solution. Through analysis of the fluorescence standard curve, the aggregates of AIEgen/chiral acid possessed 90% d-analyte, from which the enantiomeric excess (ee) value was assessed to be 80% ee. Such a result is in good agreement with that (91% d-analyte and 82% ee) by chiral HPLC analysis. Thus, this simple one-step aggregation method can serve as a preliminary screening tool for high-throughput analysis or separation of chiral chemicals.

A synergy between the push-pull electronic effect and twisted conformation for high-contrast mechanochromic AIEgens.

Mechanochromic (MC) luminogens in response to external stimulus have shown promising applications as pressure sensors and memory devices. Meanwhile, research on their underlying mechanism is still in the initial stage. Here, three pyridinium-functionalized tetraphenylethylenes bearing n-pentyloxy, hydrogen and nitro groups, namely TPE-OP, TPE-H and TPE-NO, are designed to systematically investigate the influence of the push-pull electronic effect and molecular conformation on MC luminescence. Upon anisotropic grinding and isotropic hydrostatic compression, TPE-OP with strong intramolecular charge transfer (ICT) affords the best MC behavior among them. Analysis of three polymorphs of TPE-H clearly indicates that planarization of the molecular conformation plays an important role in their bathochromic shifts under mechanical stimuli. Theoretical calculations also verify that high twisting stress of AIEgens can be released under high pressure. This study presents a mechanistic insight into MC behaviour and an effective strategy to achieve high-contrast MC luminescence.

Enantioselective recognition of chiral acids by supramolecular interactions with chiral AIEgens.

Novel chiral AIEgens bearing optically pure amino groups were synthesized and showed excellent discrimination for a series of chiral acidic compounds and amino acids. Interestingly, after supramolecular assembly with 4-sulfocalix[4]arene, the obtained complexes showed enhanced enantioselectivity for chiral acids.

Substitution Activated Precise Phototheranostics through Supramolecular Assembly of AIEgen and Calixarene.

Photodynamic therapy (PDT) is a promising noninvasive therapeutic technique and has attracted increasing interests in preclinical trials. However, the translation from laboratory to clinic often encounters the problem of undesired dark cytotoxicity of photosensitizers (PSs). Now, this challenge can be addressed by cascaded substitution activated phototheranostics using the host-guest strategy. Through electrostatical complexation of pyridinium-functionalized tetraphenylethylene, namely, TPE-PHO, and water-soluble calixarene, the dark cytotoxicity of TPE-PHO is dramatically inhibited. The nanoassemblies of the complex show enhanced biocompatibility and selectively locate at the cytoplasm in vitro. When TPE-PHO is competitively displaced from the cavity of calixarene by 4,4'-benzidine dihydrochloride at the tumor site, its dark cytotoxicity and photoactivity in tumor tissue are restored to give efficient PDT efficacy under light irradiation. The result from cell imaging reveals that TPE-PHO undergoes translocation from cytoplasm to mitochondria to kill the cancer cells during the cascaded supramolecular substitution process. In vivo tumor imaging and therapy are successfully implemented to evaluate the curative effect. Such a supramolecular strategy avoids tedious molecular synthesis and opens a new venue to readily tune the PS behaviors.

Direct Construction of Acid-Responsive Poly(indolone)s through Multicomponent Tandem Polymerizations.

Multicomponent polymerizations (MCPs) as a burgeoning field in polymer chemistry has proved to be a powerful and popular tool for the synthesis of functional polymer materials with diverse and complex structures. To explore the general applicability of MCPs and enrich the product structures of MCPs, multicomponent tandem polymerizations (MCTPs) with great synthetic simplicity and efficiency were pursued. In this work, MCTPs of N-(2-iodophenyl)-3-phenyl-N-tosylpropiolamide, aromatic terminal alkynes, and diamines were explored through combining Sonogashira coupling and Michael addition reaction in a one-pot procedure. The MCTPs could proceed efficiently and conveniently under mild conditions with Pd(PPh3)2Cl2, CuI, and i-Pr2NEt, affording 12 poly(indolone)s with unique structures and high Mws (up to 30400 g/mol) in high yields (up to 97%). The poly(indolone)s possess a unique acid-triggered fluorescence "turn-on" response which could realize specific detection of CF3SO3H from other inorganic and organic acids through a rapid acid-catalyzed reaction from enamine to ketone.

Dual fluorescence of tetraphenylethylene-substituted pyrenes with aggregation-induced emission characteristics for white-light emission.

This article presents a new strategy to achieve white-light emission from single tetraphenylethylene-substituted pyrenes (TPE-Pys) with aggregation-induced emission (AIE) characteristics. TPE-Pys were synthesized by a Pd-catalyzed coupling reaction of a boronic acid or pinacol ester of pyrene and tetraphenylethylene (TPE) derivatives and showed multicolor emission by introducing different substituents on the phenyl rings of TPE. TPE-Pys with a TPE unit at the 1-position and asymmetric TPE units at 2,7-positions show dual fluorescence in THF/water mixtures to realize white-light emission with CIE coordinates of (x = 0.30 and y = 0.41) and (x = 0.21 and y = 0.16), respectively. The structure-property relationship of TPE-Pys were investigated to elucidate the origin of the white emission. The results showed that due to the weak electronic interaction of pyrene and its chromophoric units at the 2,7-positions and the constraint of the rotation of the TPE unit at the 1-position of pyrene, each component can exhibit its own emission color. The combination of appropriate colors gives rise to white-light emission. Such a principle of molecular design may open a new avenue for preparing advanced multicolor and multifunctional optical materials for organic electronics.

AIE-Active Tetraphenylethylene Cross-Linked N-Isopropylacrylamide Polymer: A Long-Term Fluorescent Cellular Tracker.

There is a great demand to understand cell transplantation, migration, division, fusion, and lysis. Correspondingly, illuminant object-labeled bioprobes have been employed as long-term cellular tracers, which could provide valuable insights into detecting these biological processes. In this work, we designed and synthesized a fluorescent polymer, which was comprised of hydrophilic N-isopropylacrylamide polymers as matrix and a hydrophobic tetraphenylethene (TPE) unit as AIE-active cross-linkers (DDBV). It was found that when the feed molar ratio of N-isopropylacrylamides to cross-linkers was 22:1, the produced polymers demonstrated the desirable LCST at 37.5 °C. And also, the temperature sensitivity of polymers could induce phase transfer within a narrow window (32-38 °C). Meanwhile, phase transfer was able to lead the florescent response. And thus, we concluded that two responses occur when one stimulus is input. Therefore, the new cross-linker of DDBV rendered a new performance from PNIPAm and a new chance to create new materials. Moreover, the resulted polymers demonstrated very good biocompatibility with living A549 human lung adenocarcinoma cells and L929 mouse fibroblast cells, respectively. Both of these cells retained very active viabilities in the concentration range of 7.8-125 µL/mg of polymers. Notably, P[(NIPAm)22-(DDBV)1] (P6) could be readily internalized by living cells with a noninvasive manner. The cellular staining by the fluorescent polymer is so indelible that it enables cell tracing for at least 10 passages.

Water-Soluble Fluorescent Probes for Selective Recognition of Lysine and Its Application in an Object Carry-and-Release System.

A water-soluble fluorescent probe PEG-TPA-5' was synthesized, which shows an excellent selectivity to detect Lys in aqueous phase. An object carry-and-release system is established by applying PEG-TPA-5' as carrier and Lys as chemical stimulating source.

Study of Red-Emission Piezochromic Materials Based on Triphenylamine.

Two conjugated molecules based on triphenylamine and 1,3-indandione have been synthesized by employing Knoevenagel condensation. Both materials demonstrated aggregation-induced emission behavior, and solvato- and piezochromic properties. These red luminescence materials are able to respond to F- and I- sensitively. The emission wavelength changed by almost 100 nm in the presence of F- and I- , and could be observed by the naked eye under daylight and UV light.